Hmm, if you want to apply it to all notes, it’s doable, albeit a little crudely.
Select all notes (Ctrl+A) and use the + and – keys to adjust velocity in steps (I don’t know exactly how big these steps are).
There’s currently no way to directly enter numerical values for velocity or anything, and there’s also no logical selection thingy with which you could select, e.g., all notes with velocity levels 36-100, or add +5 to all notes’ velocities.
.
